This invention relates to an open-loop mechanism for controlling the actuation of a slide out room used on mobile living quarters (such as a recreational vehicle).
The width of mobile living quarters, such as recreational vehicles, is limited to that which may be accommodated for travel on the highways. Accordingly, when the mobile living quarters is parked for use, it is desirable to be able to expand the living quarters, to increase the available living area. Slide out rooms have become popular to effect expansion of the available living area of such mobile living quarters. These slide out rooms are retracted into the main living area when the vehicle is moved during travel, and extended from the main living quarters to provide additional living space when the mobile living quarters is parked for use. Slide out rooms are typically mounted on telescoping tubes which are mounted on the frame supporting the main living area, and are actuated by hydraulic rams, electric motors, or similar actuation devices. Typically, two or more such actuation devices are required. Slide out rooms are only semi-rigid. Furthermore, the two or more actuators are often not symmetrically located with respect to the slide out room, because placement of the actuators must accommodate wheel wells and other structural components of the mobile living quarters. It is thus desirable to synchronize operation of the actuators. It is also desirable to be able to control the xe2x80x9croom outxe2x80x9d and xe2x80x9croom inxe2x80x9d positions for the actuators to assure that the room is fully extended across its entire length when the room is extended for use, and to assure that it is fully retracted across its entire length when the room is retracted to permit the mobile living quarters to be moved. Failure to fully extend or fully retract the slide out room across its entire length may permit gaps to occur between the seals that seal the slide out room to the main living quarters, thus permitting moisture to leak into the unit. Failure to synchronize properly the motion of the actuators may cause undesirable deflection across the length of the room, again resulting in damage to the room or the vehicle, seal problems, and unsightly appearance of the room.
The present invention provides an open-loop synchronization system for a slide out room which synchronizes movement of the room during extension and retraction of the room without using position feedback from the extendable members supporting the room or the motors driving the extendable members. The motors used have known output characteristics which depend upon the motor input. The controller provides synchronized output signals to the motors to cause synchronized movement of the motors, and therefore synchronized movement of the extendable members. The xe2x80x9cinxe2x80x9d stop and xe2x80x9coutxe2x80x9d stop positions of the extendable members may be set during initialization of the system, and stored by the controller. Accordingly, by comparing the output signals provided to the motors during extension and retraction to the stored data corresponding to desired xe2x80x9cinxe2x80x9d and xe2x80x9coutxe2x80x9d stop positions, the system automatically stops the motors when the stop positions are reached, without feedback.
In another embodiment of the invention, stop devices which provide feedback to controller (or the operator) are used. In this embodiment, only open-loop synchronization of the motors is provided.